Covalent functionalization of two-dimensional group 14 graphane analogues

Abstract

The sp3-hybridized group 14 graphane analogues are a unique family of 2D materials in which every atom requires a terminal ligand for stability. Consequently, the optical, electronic, and thermal properties of these materials can be manipulated via covalent chemistry. Herein, we review the methodologies for preparing these materials, and compare their functionalization densities to Si/Ge(111) surfaces and other covalently terminated 2D materials. We discuss how the electronic structure, optical properties, and thermal stability of the 2D framework can be broadly tuned with the ligand identity and framework element. We highlight their recent application in electronics, optoelectronics, photocatalysis, and batteries. Overall, these materials are an intriguing regime in materials design in which both surface functionalization and solid-state chemistry can be uniquely exploited to systematically design properties and phenomena.

Customizing H3Sb3P2O14 nanosheet sensors by reversible vapor-phase amine intercalation

“…Furthermore, cycling experiments revealed that the modification is a reversible process, which allows for a versatile adaptive control of the materials' properties. This is a clear advantage compared to non-reversible covalent modification 12,17 of layered materials or sophisticated electrochemical control requiring external power supply and in most cases inert gas conditions. 18 Furthermore, patterning experiments indicate that the amine replacement method can be employed to create more complex structures coupled with area-resolved intercalation and etching.…”

“…outstanding and diverse properties in their pristine form, tailoring and fine-tuning their properties in a rational manner for applications and processing is still challenging. [12][13][14] As of now, there are five main strategies for modifying the physical and chemical properties of the nanosheets. These approaches include covalent functionalization, 12,[15][16][17] intercalation and ion exchange, 18,19 morphology control, [20][21][22][23] nanoparticle decoration 24,25 and elemental substitution.…”

“…[12][13][14] As of now, there are five main strategies for modifying the physical and chemical properties of the nanosheets. These approaches include covalent functionalization, 12,[15][16][17] intercalation and ion exchange, 18,19 morphology control, [20][21][22][23] nanoparticle decoration 24,25 and elemental substitution. 26,27 So far, postsynthetic tuning of the nanosheet properties over a broad range is only possible with covalent functionalization, electrochemical 28,29 and soft chemical intercalation, as well as ion exchange methods.…”

Dimensionality Concept in Solid‐State Reactions: A Way to Control Synthesis of Functional Materials at the Nanoscale

“…Thus, in all the 3 systems, the bottom‐up synthesis of MAl 2 X 2 proceeds as a sequence of 1D processes (1) and (2). The sequence does not necessarily stop there: the M layers in MA 2 X 2 phases can potentially be etched, similar to MX 2 phases; [ 7,24,25 ] the octahedral interstitial sites in the [AX] 2 bilayers can accommodate small ions. [ 26,38 ] As a matter of fact, sequential 1D processes are used to produce high‐power capacitors: [ 10 ] first, layered MAX phases such as Ti 2 AlC are etched into MXenes such as Ti 2 CT x (T x are surface functional groups) by selective extraction of the Al layer with HF treatment; then Ti 2 CT x is activated by Na + intercalation which expands the interlayer distance.…”

“…However, covalent modification of layered structures, that is, their transformation involving formation and/or breaking of covalent bonds, makes an important class of topotactic reactions—for instance, design of interlayer spaces in silicates. [ 22 ] In particular, covalent functionalization dominates the chemistry of buckled 2D‐Xenes [ 23 ] —elemental counterparts of graphene such as silicene (X = Si) and germanene (X = Ge)—and their derivatives: [ 7,24,25 ] 1D reactions of metalloxenes MX 2 —intercalated multilayer 2D‐Xenes—etch the metal M (but do not affect the covalent XX bonds) to produce stacks of graphane analogues with various substituents forming covalent bonds with the 2D‐Xene lattice.…”